When Los Angeles voters choose between incumbent Mayor Jim Hahn and challenger Antonio Villaraigosa in the city’s May 17 nonpartisan runoff election, a political judgment will also be rendered on what many consider the most successful and powerful of urban labor movements.

The Los Angeles County Federation of Labor, which for the past decade has been the engine of a labor-Latino alliance that has boosted a scorecard’s worth of progressive candidates into local office, looks this time like it’s chosen the wrong side. Villaraigosa, who in the last Los Angeles Times poll was floating eighteen points above the scandal-plagued incumbent, is considered to be the most pro-labor pol west of the Mississippi. The former union organizer and Southern California ACLU president had a perfect union voting record when he served as speaker of the California Assembly. The County Fed poured more than $1 million into his race when he ran against Hahn in 2001, and then supported him again a year later when he won a City Council seat.

But this time around, the local federation of more than 350 unions snubbed Villaraigosa and endorsed the more centrist Hahn. The union leadership made the move in exchange for the Mayor’s support of labor’s political wish list and as part of a deal to promote the Mayor’s job-rich $11 billion airport expansion plan (which Villaraigosa opposes). As a quid pro quo Hahn appointed County Fed leader Miguel Contreras and other union allies to important city commissions.

The expedient alliance with Hahn, however, is coming back to haunt labor. In the March primary election a plurality of union households ignored their leadership’s endorsement and voted for Villaraigosa. “Part of it is we are a victim of our own success,” Contreras explained to the press. “After all those years of telling people to vote for Antonio, it’s hard to tell them to vote for someone else.” And as the hard-fought runoff goes into the home stretch, things have gotten stickier. With Villaraigosa garnering the endorsement of major Latino, black and environmental leaders, as well as the local Democratic Party, John Kerry, and most of all the other major candidates who were defeated in the primary, just about the only institutional support left for Hahn comes from the labor federation.

Though possessed of a soporific governing style, Hahn is a ferocious campaigner who in 2001 didn’t flinch from smearing Villaraigosa as somehow connected to crack dealing. In these final weeks, Hahn has again chosen to go down and dirty. As former city attorney he imposed several antigang injunctions, and now his campaign is focusing on how the local ACLU, when led by Villaraigosa, sued to stop what it considered to be unconstitutional measures. The Hahn campaign has suggested that Villaraigosa led this action on behalf of the targeted gangs, not on constitutional issues. And in a move that surprised even the most cynical observers, Hahn recently announced his endorsement of a new ballot initiative that would restore a Christian cross to the LA County official seal. The cross was removed recently after the ACLU threatened to sue. The mayor’s endorsement of this fringe measure is aimed not only at rallying the conservative suburban vote but also at positioning Villaraigosa as antifaith.

Hahn’s final television ad barrage is expected to focus on intensely negative themes, painting Villaraigosa as pro-gang, anticop and antireligious. With the County Federation of Labor serving as Hahn’s last significant reserve, union money could very well end up financing those attacks. At a minimum, local labor’s political imprimatur is already indelibly stamped on Hahn’s negative campaign. “This would be a good time for us to be taking an extended vacation in Tahiti,” darkly joked one top-level labor official opposed to the Hahn endorsement. “How do you explain to your rank and file that their dues are being used to beat up the guy they want to vote for?”

At a time when the national labor movement is going through a highly public internal debate over where to put its emphasis–on organizing or supporting political campaigns–what happens in LA is crucial. Says the labor official: “It doesn’t make much sense to spend all that money on candidates if at a minimum you’re not spending it on the right ones, does it?”